Excitation system for dynamoelec



RGE. 22,154

Aug. 4, 1942.

A. MANDL EXCITATION SYSTEM FOR DYNAMOELETRIC MACHINES Original FiledJan. 25, 1937 W; .a g mm P t by 171M Reissued Aug. 4, 1942 EXCITATIONSYSTEM FOR DYNAMOELEC- TRIO MAOHINES Arthur Mandl, Shefiield, England,assignor to General Electric Company, a corporation of New York OriginalNo. 2,165,976, dated July 11, 1939, Serial No. 122,243, January 25,1937.

February 1'7, 1936.

12 Claims.

My invention relates to excitation systems for dynamo-electric machinesand more particularly to self-excitation circuits for dynamo-electricmachines of the synchronous type.

Because of the high efliciency and the facility of operation ofelectronic discharge apparatus of the type employing ionizable mediumsuch as gases or vapors, there has been a tendency to employ thesedevices in excitation circuits for dynamo-electric machines of largeratings. Since there are particular advantages to be derived by the useof electronic discharge apparatus in installations of this nature, itbecomes increasingly important to employ apparatus of high efliciencyand of reasonable proportion relative to the main or principalapparatus. In order to eliminate the necessity for elaborateinstallations of auxiliary apparatus and control apparatus in connectionwith the operation of electric generators of large rating such asturbo-alternators and waterwheel driven generators, there has'beenevidenced a decided need for excitation systems capable of energizingthe field winding of the machines independently of any auxiliary sourceof current. For example, in the case of isolated hydro-electric plantswhere elaborate and complicated auxiliary or control equipment wouldnecessitate frequent inspections and disproportionate initialinvestment, it is highly important and desirable to provide electricvalve apparatus which is simple in ccnstructon and operation forsupplying the excitation of the main generators during the startingoperation independently of any auxiliary source of energy. Due to thefact that the main generators are not designed to maintain a substantialresidual magnetism and due to the fact that the operating conditionsimmediately preceding the starting operation may have been such that theresidual magnetism of the machine has been reduced to a substantiallyzero value, it is important to provide some auxiliary equipment wherebythe excitation of the main generator is built up to a sufficient valueto permit electric valve apparatus to be energized from the armaturewinding of the main generator.

It is an object of my invention to provide a new and improved excitationsystem for dynamoelectric machines.

It i another object of my invention to provide a new and improvedself-excitation system for a dynamo-electric machine of the synchronoustype.

It is a further object of my. invention to pro- In Germany Applicationfor reissue June 18, 1941, Serial No. 398,682

vide a new and improved self-excitation system for startingdynamo-electric machines.

In accordance with the illustrated embodiments of my invention, Iprovide a new and improved electric valve system for energizing thefield winding of a dynamo-electric machine independently of anyauxiliary source of current. The electric valve means comprises aplurality of main or principal arc discharge paths which excitation ofthe machine to a value sufficient for initiating arc discharges withinthe principal arc discharge paths. An auxiliary alternating currentgenerator having a permanent magnet field member or being of a materialof high coercive force is employed to energize the auxiliary aredischarge paths to effect energization of the field winding of the maingenerator during the starting operation. Means responsive to anelectrical condition of the field winding, such as the our- 7 rent ofthe field winding, is provided to disconnect the auxiliary generatorafter arc discharges have been established within the principal arcdischarge paths.

For a better understanding of my invention reference may be had to thefollowing description taken in connection with the accompanying drawingand its scope will be pointed out in the appended claims.

Figs. 1 and 2 represent certain embodiments of my invention as appliedto a system for energizing the field winding of a dynamo-electricmachine, and Fig. 3 represents certain operating 7 characteristics ofthe embodiment of my invention shown in Fig. 2.

Referring now to Fig. 1, my invention is diagrammatically illustratedtherein as applied to a self-excitation system for a dynamo-electricmachine I of the synchronous type having armature windings 2 and arelatively movable field winding 3. The armature windings 2 areconnected to an alternating current circuit 4 which may form a part of atransmission or distribution system. The field winding 3 may be drivenby any suitable means such as a prime mover 5 which is diagrammaticallyillustrated in the drawing.

I provide an excitation system for energizing the field winding 3 fromthe armature windings 2 comprising a transformer 6 having primarywindings 1 and secondary windings 8, and an electronic discharge device9 comprising a plurality of arc discharge paths. The electronicdischarge device 9 comprises a cathode l0, a plurality of principalanodes II, I! and I3 and a plurality of auxiliary anodes l4, I5 and I6.While for the purpose of explaining my invention I have chosen torepresent the electronic discharge means 9 as being of the typeincluding a plurality of anodes and a single cathode mounted within asingle enclosing receptacle, it should be understood that I may employ aplurality of electronic discharge devices of the type in which a singleanode and cathode are mounted within the receptacle. In order toenergize the field winding 3 of the dynamo-electric machine I during thestarting operation before the excitation of the machine I has increasedto a value suiiicient for establishing are discharges between theprincipal anodes ll, I2 and I3 and the cathode I8, I provide anauxiliary alternating current generator I! including armature windingsl8 and a field member IS. The field member l9 may be a permanent magnetor may be of material of relatively great coercive force so that uponrotation of the field winding 3 and the field member l9 by the primemover 5 during the starting operation, there will be a suificientvoltage induced in the armature windings l8 of auxiliary generator I! toestablish arc discharges between the auxiliary anodes M, [5 and I6 andthe cathode lfl to build up the excitation of the machine I.

As a means for disconnecting the auxiliary generator ll from the circuitfor the field wind,- ing 3 after electric discharges have been initiatedbetween the principal anodes ll, l2 and I3 and the cathode I3, I provideany suitable means responsive to a predetermined operating condition ofthe machine I such as an electrical condition of the field circuit. Inthe particular arrangement shown in Fig. 1 this means isdiagrammatically shown as including a current responsive deviceconnected in the field circuit and includes an actuating winding 2|connected in series relation with the field winding 3 and secondarywindings 8 of the transformer 6. The current responsive device 20includes an armature member 22 and contacts 23. While for the purpose ofillustrating my invention I have chosen to represent this means fordisconnecting the auxiliary generator l1 in accordance with the currentof the field Winding 3 of machine I, it should be understood that I mayemploy any suitable means responsive to other suitable conditions of thedynamo-electric machine I for effecting this operation.

The operation of the embodiment of my invention diagrammatically shownin Fig. 1 may be best explained by considering the excitation systemduring a starting operation. Prior to the initiation of the rotation ofthe armature member 2! the current responsive device 20 will be in theposition shown to engage the contacts 23 so that the armature windingsIB of the auxiliary alternating current generator l1 are connected tothe field winding 3 of dynamo-electric machine I through the auxiliaryanodes I4, l5 and I5 of electronic discharge device 9. Upon rotation ofthe field member IQ of the auxiliary generator I! there will be inducedin the armature windings l8 a voltage of sufiicient magniture toinitiate arc discharges between the oathode H) and the auxiliary anodesl4, l5 and I6 of the electronic discharge means 9 to supply directcurrent to the field winding 3 of machine I to build up the excitationof this machine. When the voltage of the machine I builds up to a valuesuflicient to initiate arc discharges between the cathode l0 and theprincipal anodes II, l2 and I3 there will be supplied to the fieldwinding 3 a current of increased value established by the design of thetransformer 6 and the design of machine I. After the current supplied tothe field winding 3 by the principal anodes II, l2 and" I3 increases toa predetermined value established by the design or adjustment of thecur- .rent responsive means 20, armature member 22 thereof will beraised to open the contacts 23 disconnecting the auxiliary generator I!from the field Winding 3.

An important feature of my invention is the fact that after the build upof excitation of the machine I is initiated by the auxiliary generatorH, the generator I! is disconnected from the energizing circuit for thefield winding 3. Since the auxiliary generator I? is not subjected toshort circuit conditions of the machine I which would tend to reduce theresidual magnetism of the field member l9, there is always available anauxiliary source of voltage for initiating the energization of the fieldwinding 3 during a starting operation.

Fig. 2 shows another embodiment of my invention substantially similar tothat shown in Fig. l and corresponding elements have been assigned likereference numerals. The field Winding 3 of dynamo-electric machine i isenergized through a principal electronic discharge device 24 and anassociated transformer 25. The energization of the field winding 3during the starting operation is provided by means of the auxil- 85.

iary alternating current generator I1 and an associated auxiliaryelectronic discharge device 26 and an associated transformer 21. Inorder to increase the excitation of the auxiliary generator IT tocompensate for armature reaction as the auxiliary generator I! begins tosupply current to the field winding 3 during the starting operation, Iprovide a field Winding 28 which is connected in series relation withthe field Winding 3 and electronic discharge device 28. By virtue ofthis arrangement there is provided a means for maintaining theexcitation of the auxiliary generator IT at a proper Value so that thearmature current does not materially decrease the voltage of theauxiliary generator I? during the starting operation.

The operation of the arrangement of my invention diagrammatically shownin Fig. 2 is substantially the same as that explained above inconnection with Fig. 1. The operating characteristics shown in Fig. 3may be considered relative to the operation of the auxiliary alternatingcurrent generator I! and the function which the winding 28 performs inmaintaining the excitation of this generator at a predetermined value.Curve A represents the flux of the auxiliary generator I! as a functionof the magnetomotive force, and line B represents the demagnetizingaction of the armature current flowing in windings 18 of machine IT. Theintersection of these two curves at point a represents the resultantflux in the generator I! and the distance a-b represents themagnetomotive force required to compensate for the armaturedemagnetization.

While I have shown and described my invention as applied to a particularsystem of connections and as embodying various devices diagrammaticallyshown, it will be obvious to those skilled in the art that changes andmodifications may be made Without departing from my invention,

and I, therefore, aim in the appended claims to cover all such changesand modifications as fall within the true spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a dynamo-electric machine having an armature windingand a relatively movable field winding, electronic discharge means forenergizing said field winding comprising a plurality of principal arcdischarge paths connected to be energized from said armature winding anda plurality of auxiliary arc discharge paths, an auxiliary alternatingcurrent generator having a permanent magnet field member for energizingsaid auxiliary arc discharge paths to energize said field winding inorder to increase the excitation of said dynamo-electric machine to avalue sumcient to initiate electric discharges within said principal arcdischarge paths, and means responsive to a predetermined electricalcondition of said machine for effecting energization of said fieldwinding from said principal arc discharge paths when the excitation ofsaid machine attains a predetermined value.

2. In an excitation system for a dynamo-electric machine having anarmature winding and a relatively movable field winding, the combinationof an electronic discharge means energized from said armature windingfor supplying direct current to said field winding, an auxiliaryalternating current generator having a permanent magnet field member, anauxiliary electronic discharge means interposed between said fieldwinding and said auxiliary alternating current generator for supplyingdirect current to said field winding in order to increase the excitationof said dynamo-electric machine to a value sufficient to initiateelectric discharges within said first mentioned electronic dischargemeans, and means responsive to the voltage of said armature winding foreffecting energization of said field winding from said first mentionedelectronic discharge means when the armature voltage attains apredetermined value.

3. In combination, a dynamo-electric machine having an armature windingand a field winding, means for rotating said field winding relative tosaid armature winding, electronic discharge means energized from saidarmature winding for energizing said field winding, means for buildingup the excitation of said dynamoelectric machine comprising an auxiliaryalternating current generator having a field member of high coerciveforce and an auxiliary electronic discharge means interposed betweensaid field winding and said auxiliary alternating current generator forsupplying direct current to said field winding prior to the initiationof an arc discharge within said first mentioned electronic dischargemeans, and means responsive to the voltage of said armature winding forconnecting said first mentioned electronic discharge means to said fieldwinding when the armature voltage of said machine attains apredetermined value.

4. In combination, a dynamo-electric machine having an armature windingand a field winding, means for rotating said field winding relative tosaid armature winding, electronic discharge means energized from saidarmature winding for energizing said field winding, means for energizingsaid field winding during a starting operation comprising an auxiliaryalternating current generator having a permanent magnet field member andan auxiliary electronic discharge means interposed between said fieldwind ing and said auxiliary alternating current generator for energizingsaid field winding during said starting operation, and means responsiveto an operating condition of said dynamo-electric machine fordisconencting said auxiliary generator from said field winding.

5. In combination, a dynamo-electric machine having an armature windingand a field winding, means for rotating said field winding relative tosaid armature winding, electronic discharge means energized from saidarmature winding for supplying direct current to said field. winding, anauxiliary alternating current generator driven by said first mentionedmeans and including a field member having a high coercive force and afield winding associated with said field member, an auxiliary electronicdischarge means interposed between said first mentioned field windingand said auxiliary generator for supplying direct current to said firstmentioned field winding during a starting operation, said field windingof said auxiliary generator being proportioned to assure a positivebuild-up of the excitation of said auxiliary generator to establishelectric discharges within said auxiliary electronic discharge meansduring the starting operation, and means responsive to an electricalcondition of said first mentioned field winding to disconnect saidauxiliary generator and said auxiliary electronic discharge means fromsaid first-mentioned field winding, after the excitation of saiddynamo-electric machine has increased to a predetermined value.

6. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, and auxiliary means mechanically driven by the generator forsupplying excitation to the field winding during the starting period.

7. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, and an auxiliary generator driven by the first mentionedgenerator for supplying excitation to the field winding during thestarting period.

8. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, an auxiliary synchronous generator driven by the firstmentioned generator, and means for converting the output of saidauxiliary generator to direct current for exciting said field windingduring the starting period while the voltage of the first mentionedgenerator is building up.

9. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, an auxiliary synchronous generator driven by the firstmentioned generator, said auxiliary generator having a permanent magnetrotor, and means for converting the output of said auxiliary generatorto direct current for exciting said field winding during the startingperiod while the voltage of the first mentioned generator is buildingup.

10. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, an auxiliary synchronous generator driven by the firstmentioned generator, and rectifier means for converting the output ofsaid auxiliary generator to direct current, said rectifier means beingconnected to said field winding for exciting it during the startingperiod.

11. A system for self-excitation of an alternating current generatorhaving a direct current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldwinding, an auxiliary synchronous generator driven by the firstmentioned generator, rectifier means for converting the output of saidauxiliary generator to direct current, said rectifier means beingconnected to said field winding for exciting it during the startingperiod, and means for disconnecting the rectifier means from the fieldwinding.

12. A system for self-excitation of an alternating current generatorhaving a direct-current field winding comprising means energized fromthe generator for supplying direct-current excitation to the fieldWinding, an auxiliary synchronous generator driven by the firstmentioned generator, said auxiliary generator having a permanent magnetrotor, rectifier means for converting the output of said auxiliarygenerator to direct current, said rectifier means being connected tosaid field winding for exciting it during the starting period, and meansfor disconmeeting the rectifier means from the field winding.

ARTHUR MANDL.

